This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise explicitly indicated herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section. Abbreviations that may be found in the specification and/or the drawing figures are defined below, prior to the claims.
Base stations connect wireless devices, called user equipment herein, to wireless networks. Base stations have different names depending on the technology being used. For UTRAN, for instance, the base station is a base transceiver station (BTS) and a NodeB, and a radio network controller (RNC) controls the NodeB. For E-UTRAN, the BTS and NodeB are replaced by an eNB, which also has functionality previously implemented in the RNC. The eNB is the base station for E-UTRAN. The base stations implement transceivers for whatever the air interface is, such as long term evolution (LTE), code division multiple access (CDMA), and the like.
A transceiver contains typically a transmitter and a receiver. The transmitter uses a power amplifier to amplify signals from a low level to a level suitable for transmission over long distances. Power amplifiers produce a non-linear output, which creates distortion such as intermodulation (IM) products in the output. One technique for dealing with the non-linear output is to pre-distort the input to a power amplifier so that the output of the power amplifier is approximately linear over some range of power output. Digital predistortion (DPD) is one commonly used technique to perform this predistortion.
Radio units implemented in base stations undergo strict factory tests to rule out typical transceiver impairments. These tests will normally include 3GPP specified intermodulation product results. Even with these tests, multiple radio units are still failing 3GPP specifications in the field.
Unless a customer using the radio units performs specific tests regularly on these units, no one will know of these types of impairments. These tests cost a lot of money to the customer as well as to the manufacturer of the radio units. These costs include sending a technician to the cell site, perhaps decommissioning the radio (e.g., BTS), transmitting waveforms, and observing the produced intermodulation products with a spectrum analyzer.
Added test times will then reduce revenue to the customer, as the radio is offline during the tests. This also may cause an interrupt in service for wireless users in the area. Lastly, it is extremely difficult to take a spectrum analyzer to a site due to its size and most likely the analyzer has to be battery powered if power plugs are not found in the cell site. It would be beneficial to improve upon this.